A suede-like artificial leather having a surface having a raised nap made of a microfiber has a soft feeling, excellent physical properties, and an elegant appearance, and hitherto the leather has widely been used for clothing, furniture, vehicle interior materials, and others. Such a suede-like artificial leather, which has a surface having a raised nap made of a microfiber, has a structure wherein a sheet-form object made of the microfiber is impregnated with an elastic polymer. Thus, the artificial leather has the following problem: when the artificial leather is actually used, the leather is worn away so that the filaments of the microfiber are entangled with each other to turn to pills, that is, the so-called pilling is generated. Against this problem, various suggestions have been made so far.
Specifically, for the prevention of the pilling of a suede-like artificial leather, suggested is a method about a suede-like artificial leather composed of an entangled nonwoven fabric made of polyester microfiber bundles having a monofilament fineness of 0.2 to 0.005 dtex, and an elastic polymer, wherein silica having a particle diameter of 100 nm or less is incorporated into the polyester microfiber in a proportion of 0.5 to 10% by mass to the microfiber (Patent Document 1). However, according to this suggestion, it is necessary to incorporate inorganic particles of silica into the polyester microfiber. Thus, this suggestion has the following problem: in spinning into the fiber, coarse particles wherein the inorganic particles aggregate secondarily are generated; thus, the filtration pressure is raised, so that thread breakage is caused; it is therefore difficult to continue the spinning over a long period. Additionally, this suggestion has another problem that when a raised nap is formed in the surface of the artificial leather, filaments in the nap-raised regions are cut so that the length of the raised nap turns short, whereby an elegant raised nap cannot be formed.
Suggested is also a method about a suede-like artificial leather made of a polyethylene terephthalate microfiber having a monofilament fineness of 0.5 dtex or less, and a polyurethane resin, wherein the intrinsic viscosity of the polyethylene terephthalate is set into the range of 0.57 or more and 0.63 or less, thereby reducing the strength of the polyethylene terephthalate microfiber not to cause pilling (Patent Document 2). Although this suggestion can overcome pilling by setting the intrinsic viscosity of the microfiber into a low value and thus lowering the thread strength, this suggestion has a problem that the artificial leather itself is deteriorated in physical properties such as tensile strength and tear strength.
Separately, suggested is a long-fiber nonwoven fabric made of a peeling-separation type composite fiber wherein inorganic particles, a silicone oil and others are added to at least one component of a polyamide polymer and a polyester polymer (Patent Document 3). However, in this suggestion, the silicone oil is added to make easy the separation of the peeling-separation type composite fiber, and the inorganic particles are added to adjust the coloring effect and the cross sectional shape of the fiber filaments. Furthermore, in working examples of Patent Document 3, specifically, neither silicone oil nor inorganic particles are added to any polymer, so that no pilling-resistance is expressed.